Evaluating motion of pancreatic tumors and anatomical surrogates using cine MRI in 0.35T MRgRT under free breathing conditions

Lewis, Benjamin; Guta, Anamaria; Shin, Ju Hye; Ji, Zhen; Kim, Jin Sung; Kim, Sang Woo

doi:10.1002/acm2.13930

Cited by 8 publications

(1 citation statement)

References 36 publications

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“…The tumor positioning methods can be divided into two major techniques: direct and indirect [ 24 ]. Direct methods are those that use imaging systems to directly track the tumor position, and such systems are kilovolt X-ray imaging-based methods [ 25 , 26 , 27 , 28 ], magnetic resonance (MR) imaging-based approaches [ 29 ], electromagnetic sensing systems [ 30 , 31 ], and ultrasound-based techniques [ 32 , 33 , 34 , 35 ]. In indirect position tracking technique, the motion trajectory is tracked using a surrogate target that is highly associated with the tumor motion, for instance, thoracoabdominal surface displacement tracking using surface optical trackers.…”

Section: Introductionmentioning

confidence: 99%

Ultrasound Imaging with Flexible Array Transducer for Pancreatic Cancer Radiation Therapy

Huang

Hooshangnejad

China

et al. 2023

Cancers

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Pancreatic cancer with less than 10% 3-year survival rate is one of deadliest cancer types and greatly benefits from enhanced radiotherapy. Organ motion monitoring helps spare the normal tissue from high radiation and, in turn, enables the dose escalation to the target that has been shown to improve the effectiveness of RT by doubling and tripling post-RT survival rate. The flexible array transducer is a novel and promising solution to address the limitation of conventional US probes. We proposed a novel shape estimation for flexible array transducer using two sequential algorithms: (i) an optical tracking-based system that uses the optical markers coordinates attached to the probe at specific positions to estimate the array shape in real-time and (ii) a fully automatic shape optimization algorithm that automatically searches for the optimal array shape that results in the highest quality reconstructed image. We conducted phantom and in vivo experiments to evaluate the estimated array shapes and the accuracy of reconstructed US images. The proposed method reconstructed US images with low full-width-at-half-maximum (FWHM) of the point scatters, correct aspect ratio of the cyst, and high-matching score with the ground truth. Our results demonstrated that the proposed methods reconstruct high-quality ultrasound images with significantly less defocusing and distortion compared with those without any correction. Specifically, the automatic optimization method reduced the array shape estimation error to less than half-wavelength of transmitted wave, resulting in a high-quality reconstructed image.

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Section: Introductionmentioning

confidence: 99%

Ultrasound Imaging with Flexible Array Transducer for Pancreatic Cancer Radiation Therapy

Huang

Hooshangnejad

China

et al. 2023

Cancers

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Evaluating motion of pancreatic tumors and anatomical surrogates using cine MRI in 0.35T MRgRT under free breathing conditions

Lewis

Guta

Shin

et al. 2023

J Applied Clin Med Phys

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Treatment tolerability is a significant limitation to pancreatic cancer treatment with radiotherapy due to proximity to highly radiosensitive organs and respiratory motion necessitating expanded target margins. Further, pancreatic tumors are difficult to visualize on conventional radiotherapy systems. Surrogates are often used to locate the tumor but are often inconsistent and do not provide strong positional relations throughout the respiratory cycle. This work utilizes a retrospective dataset of 45 pancreatic cancer patients treated on an MR-Linac system with cine MRI acquired for real-time target tracking. We investigated intra-fraction motion of tumors and two abdominal surrogates, leading to prediction models between the tumor and surrogate.Patient specific motion evaluation and prediction models were generated from 225 cine MRI series acquired during treatment. Tumor contours were used to evaluate the pancreatic tumor motion. Linear regression and principal component analysis (PCA) based models were used to predict tumor position from the anterior-posterior (AP) motion of the abdominal surface, the superior-inferior (SI) motion of the diaphragm, or a combination. Models were evaluated using mean squared error (MSE) and mean absolute error (MAE). Contour analysis showed the average pancreatic tumor motion range was 7.4 ± 2.7 mm and 14.9 ± 5.8 mm in the AP and SI directions, respectively. The PCA model had MSE of 1.4 mm 2 and 0.6 mm 2 , for the SI and AP directions, respectively, with both surrogates as inputs for the models. When only the abdomen surrogate was used, MSE was 1.3 mm 2 and 0.4 mm 2 in the SI and AP directions, while it was 0.4 mm 2 and 1.3 mm 2 when only the diaphragm surrogate was used. We evaluated intra-fraction pancreatic tumor motion and demonstrated prediction models between the tumor and surrogate. The models calculated the pancreatic tumor position from diaphragm, abdominal, or both contours within standard pancreatic cancer target margin, and the process could be applied to other disease sites in the abdominothoracic cavity.

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Analysis of sagittal plane cine magnetic resonance imaging for measurement of pancreatic tumor residual motion during breath hold and evaluation of gating margins used in radiotherapy treatment

Phipps,

Robinson,

George

et al. 2024

J Applied Clin Med Phys

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Background and purposeIn pancreatic radiotherapy, residual tumor motion during treatment increases the risk of toxicity. Cine imaging acquired during magnetic resonance guided radiotherapy (MRgRT) enables real‐time treatment gating in response to anatomical motion, which can reduce this risk; however, treatment gating can negatively impact the efficiency of treatment. This study aimed to quantify the extent of residual tumor motion during breath hold and evaluate the appropriateness of the treatment gating margins used in current clinical practice.Materials and methodsCine imaging acquired during pancreatic MRgRT of 11 patients on the ViewRay MRIdian was analyzed. The total duration of treatment analyzed was 12 h 13 min. Improved methods for processing and analyzing cine imaging were developed: breath holds were systematically separated with frequency analysis, residual motion was measured with consideration of both the tracking structure contour and centroid, and residual motion measurements were supported by phantom measurements of image scaling, resolution, and noise. Residual motion was measured at angles 0°, 45°, 90°, and 135° to the superior‐inferior (SI) direction. Total residual motion was measured by combining directional measurements.ResultsThe minimum tracking structure displacement resolvable through cine imaging was found to be 1.5 mm; therefore, residual motion analysis was limited to 1.5 mm spatial resolution. Total residual motion was contained within margins ±1.5, ±3, and ±4.5mm with mean percentage frequencies of 97.0%, 91.1%, and 67.8%. Most residual motion was observed in the SI direction, and significantly more residual motion was measured for the tracking structure contour than the centroid.ConclusionThe results demonstrate that patients are largely able to maintain breath hold positions to within a 3 mm margin, thus provide evidence that supports the use of a 3mm gating margin in clinical practice. Residual motion frequently exceeded 1.5 mm so a reduction in gating margin would have an undesirable impact on treatment efficiency.

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Evaluating motion of pancreatic tumors and anatomical surrogates using cine MRI in 0.35T MRgRT under free breathing conditions

Cited by 8 publications

References 36 publications

Ultrasound Imaging with Flexible Array Transducer for Pancreatic Cancer Radiation Therapy

Ultrasound Imaging with Flexible Array Transducer for Pancreatic Cancer Radiation Therapy

Evaluating motion of pancreatic tumors and anatomical surrogates using cine MRI in 0.35T MRgRT under free breathing conditions

Analysis of sagittal plane cine magnetic resonance imaging for measurement of pancreatic tumor residual motion during breath hold and evaluation of gating margins used in radiotherapy treatment

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